1. Field of the Invention
This invention relates to rotary lawn or grass mowers, and more particularly, to mulching mowers having a plurality of rotary cutting blades, such as mowing decks commonly found on lawn tractors, garden tractors and commercial mowing tractors. The invention provides a new and improved mulching deck as well as a kit for converting an existing mowing deck into an improved mulching deck.
2. Description of Related Art
The conventional lawn tractor, garden tractor, or commercial mowing tractor has a plurality of rotary cutting blades, typically numbering from two to five, although larger commercial models may include many more. They are used to mow a variety of types of grass under a variety of conditions: household lawns, landscaping lawns adjacent public and corporate buildings, golf course fairways and roughs, fields, and weeds alongside roadways, to name a few.
The usual mowing tractor cuts the grass and discharges the clippings either into a grass collector or onto the grass beside the mowing deck's discharge chute. When the clippings are collected, frequent dumping of the grass collector, along with subsequent disposal of the clippings, entails a considerable cost in time and money, especially when the mowing has been commercially contracted.
In those instances in which the grass is not collected, other problems arise. Because of the danger of injury to people or damage to property caused by the forcible ejection of hard objects from the mowing deck, most mowing decks are installed with a spring-biased flap covering the discharge chute. As a result, the clippings are deposited in dense windows adjacent the discharge chute of the mowing deck. When the grass is heavy or wet, the clippings form grass-smothering clumps which often kill the underlying grass, producing bare spots which are unsightly and which promote erosion.
It is ecologically desirable, and more cost efficient, to mulch the clippings. As mulch, the clippings are directly absorbed into the lawn or field, returning to the soil the nutrients extracted therefrom for their growth, thus promoting lush growth as well as preventing the aforesaid erosion. Mulching the clippings also removes the necessity to bag and dispose of the clippings.
In the past, the conversion to mulching mowers of hand-propelled, discharge-type lawn mowers has received much attention as a field of invention.
Williams, U.S. Pat. No. 2,685,774, enclosed a reel-type lawnmower with a flexible screen having cutter ribs mounted internally therein. The reel blades coact with the ribs in the manner of scissors to mulch the clippings.
Davis et al, U.S. Pat. No. 2,836,024, provide a rotary cutting blade which cuts standing grass and lifts the clippings above the plane of the blade. A plurality of stationary blades are located immediately above the rotary blade which scissor the clippings into mulch.
Halsten, U.S. Pat. No. 3,959,954, lifts the clippings into an apertured housing having a plurality of free-swinging flails therein. The flails beat the clippings until they are comminuted sufficiently to pass through the apertures as mulch.
Hass, U.S. Pat. No. 4,083,166, fixes a rotary disc with cutting blades coaxially above a rotary cutting blade. The rotary cutting blade cuts the grass and lifts the clippings through large openings in the disc into the path of the disc's cutting blades.
Jackson et al, U.S. Pat. No. 4,189,903, supplying a mulching attachment for single-bladed rotary mowers. The attachment comprises a linear mounted internally of the mower housing above the rotary blade. The liner is continuous around its periphery, thereby closing any discharge chute the mower may have. Guide vanes are located internally of the liner to deflect or direct the clippings inwardly and downwardly. A special rotary cutting blade has an outer region which cuts the grass and lifts the clippings upwardly into contact with the guide vanes. An inner region of the blade has a sharpened cutting edge for mulching the downwardly deflected clippings followed by a downwardly directed edge for blowing the twice-cut clippings into the grass.
Paker, U.S. Pat. No. 4,189,904, converts a conventional rotary mower into a mulching mower by covering the discharge chute with a plate. The plate has a plurality of tines and openings formed thereon to mulch grass or leaves.
Thorud, U.S. Pat. No. 4,205,512, like Jackson et al, provides guide vanes, "kickers", within the mower housing to direct clippings inwardly and downwardly into a sharpened edge of the rotary cutting blade.
Szymanis, U.S. Pat. No. 4,318,268, uses a compound blade, like Jackson et al, having an outer region which cuts and lifts the clippings and an inner region which further cuts and blows the clippings downwardly into the grass. Szymanis provides a toroidal chamber around the outer periphery of the housing to direct the clippings inwardly and downwardly into the compound blade.
Israel, U.S. Pat. No. 4,890,446, affixes a mulching plate upstream of the discharge chute which, with the rotary cutting blade, scissors the clippings prior to exiting through the discharge chute.
Thorud et al, U.S. Pat. Nos. 4,951,449, and 5,090,183, disclose a plurality of kickers which deflect the clippings inwardly and downwardly into secondary contact with the rotary cutting blade for mulching, in the general manner of Jackson et al and Thorud, above.
The above-noted mulching mowers were concerned with the problems of cutting and mulching lawns, such as household lawns. These are relatively small parcels of land with fine grass specially selected for their groomed, decorative look. Multi-bladed mowers, on the other hand, while also used in groomed lawn situations, are additionally required to handle more demanding conditions. Small fields, e.g., two to five acres, as would be found in mini-estates, government installations, golf courses, etc., have a variety of grasses and weeds which need mowing as well. Often, the cycle of mowing is interrupted by other duties or prolonged periods of rain, and the field's grass becomes tall and thick, often accompanied by moisture retained on the lower portions of the grass, even after a few days of sunshine. An added burden is thus placed on multi-bladed mowing machines which the average household lawn mower never faces.
Being tall and dense presents additional problems. Bagging acres of grass is clearly very time consuming and inordinately expensive. If the cut grass and weeds are simply discharged in windrows, they tend to stifle the growth beneath them. Mulching would be desirable, if it could be attained under these extremely adverse conditions.
Multi-bladed mowers have been developed. To date, however, they have not been completely adequate for the task.
Some multi-bladed mowers concentrate on spreading the clippings more evenly. Examples include Bacon, U.S. Pat. No. 3,469,376, and Hansen et al, U.S. Pat. No. 4,502,271, both of which provide baffles and deflectors positioned to spread the discharge of the clippings over a wider area. Reilly, U.S. Pat. No. 4,543,773, places anti-blowout plates adjacent each rotary blade at the lower edge of the housing skirt to prevent windrowing due to clippings being blown out from under the housing upstream of the discharge chute.
Multi-blade mulching decks have been proposed. Exemplary are Mullet et al, U.S. Pat. No. 4,226,074, Mullet et al, U.S. Pat. No. 4,916,887, Pernia, U.S. Pat. No. 4,938,011, and the application of Thorud's concepts, discussed above, to multi-blade mowers by The Toro Company of Minneapolis, Minn.
Mullet et al ('074) provide manually operated gates which close exit channels from each of the rotary cutting blades, effectively isolating each blade in its own internal chamber. The clipped grass is recirculated within each individual chamber until comminuted into mulch by the blade which clipped it.
Mullet et al ('887) install baffles to guide all clippings from the plurality of rotary cutting blades into a separate set of mulching blades, the mulching blades being located immediately before the discharge chute.
Pernia closes the discharge chute with a panel having a plurality of fixed blades selectively mounted thereon. The clippings impact the fixed blades, are further cut, and fall to the ground.
And, The Toro Company shapes the housing to provide a separate chamber for each rotary blade to essentially isolate it from the others. Kickers, shaped and placed as described in the Thorud patents discussed above, are provided in each chamber to recirculate the clippings back into comminuting contact with the blade which initially cut the clippings.
These mulching mowers, while undoubtedly suitable for lawn-type environments, can be inadequate, when cutting tall or dense grass, especially if the grass is wet. Simply covering the discharge chute with a panel and fixed blades is often insufficient to completely mulch the volume of clippings produced by multi-bladed mowing decks. In like manner, individual blades which cut heavy weeds and subsequently chop the recirculated clippings for comminution can be overloaded. It is customary when mowing dense grass with a multi-bladed mower to use only one-third to one-half of the cutting width of the mowing deck for cutting a new path. The most upstream of the blades is the only one which is actually cutting grass. The remaining blades act principally to blow the dense clippings from the housing, while secondarily cutting grass remaining standing from the last pass. When too much grass is circulated adjacent any one blade, that blade becomes jammed and stops, causing the drive belt to pass over a stationary pulley creating heat which burns and severs the belt. Isolating each blade in its own chamber promotes blade overload.
There exists, therefore, a need for a mulching deck for multi-bladed mowers, which is capable of mulching grass under all conditions likely to be encountered, including very tall, dense, and wet grass or weeds.